major issue

:banghead: i need help , i brougt a 93 325i 4 years ago i never did any work on it everything ran fine ! perfect on gas, max speed 114 mpg coming home from chicago. :grinyes: but now for some reason my plugs have alot of carbon build up, rough idle after normal engine temp has been reached , but runs like brand new when cold . i dont notice anything while driving until i switch gears at low rpm car sputters. i know how to repair air mixture ratio on an old skool carb but this one got me beat when i disconnect the air meter sensor or the throttle sensor at normal running temp the problem stops temp. for about 1 min or so :screwy: . before i go and start buying parts i would like some advice on what sensors controls the mixture ratio. thanks

Look here first:
http://www.bimmerdiy.com/e30

Find the electronics here:
http://shark.armchair.mb.ca/~dave/BMW/e30/

allen key screw on airflow meter

how long since you changed or refiled your oil... the carbon might be because of burning oil.. with indicates old, or too litle oil in some cases

I believe that if you read the owners manual carefully you will find that the octane rating listed is RON not AKI (our US ratings) and that 93 Ron is close to 87 AKI or at least 89 AKI. I don't believe that the octane rating is your issue, as I have run numerous Bimmers including my '88 750 on 87 AKI with no issue as to performance.